Conventionally, a pH electrode is used in order to measure a pH of, for example, a sample solution used for an experiment. This pH electrode is inserted into a container in which the sample solution is put and soaked in the sample solution so as to measure the pH of the sample solution, however, an adverse effect might be brought to the experiment because a content of the sample solution attaches to the pH electrode. In addition, in case of cleaning inside of the container, if a distal end part of the pH electrode projects inside of the container, it is necessary to clean the inside of the container carefully in order to prevent breaking the pH electrode. Furthermore, if the distal end part of the pH projects inside of the container, an adhesive material easily attaches to the pH electrode so that a cleaning operation becomes complicated.
In addition, also for a recently conducted regenerative therapy wherein a cell or a part of an organ of a human being or an animal is cultivated and regenerated so as to treat a disease, the pH of a cell culture medium is measured in order to control a cultivation state in case of cultivating the cell. In measuring the pH of the cell cultivation, in case of stirring the cell culture medium, if the cell hits against the electrode, the cell gets stressed and the stress gives a bad influence on the cell cultivation. Then the arrangement of the pH electrode that does not apply stress to the cell is desirable.
For example, the patent document 1 describes a pH electrode that is arranged in a container of a culture medium. The pH electrode is inserted into the container from its side surface to measure a pH of the culture medium. Since a distal end part of the pH electrode projects indie of the container, in case of cleaning the inside of the container, it is necessary to clean the container carefully in order not to break the pH electrode. In addition, there is a problem that an adhesive material easily attaches to the pH electrode so that a cleaning operation becomes complicated. If the culture medium is stirred, there is a problem that the cell hits against the distal end part of the electrode so that the cell gets stressed.